The two serial ports used on Macintosh computers since the Macintosh Plus are
RS-422 mini-circular 8 pin connectors:
Pin Signal
1 - HSKo (Data Terminal Ready)
2 - HSKi (Clear To Send)
3 - TxD- (Transmit Data -)
4 - GND (Ground)
5 - RxD- (Receive Data -)
6 - TxD+ (Transmit Data +)
7 - GPi (General-Purpose input); connected to SCC Data Carrier
Detect (or to Receive/Transmit Clock if the VIA1 SYNC signal
is high). Not connected on the Macintosh Plus, Classic,
Classic II, LC, LC II, or IIsi.
8 - RxD+ (Receive Data +)
Looking at the end of a MALE mini-circular connector, the pins are:
6 7 8
3 4 5 The space is between pin 4 and 5
1 2
All Macintosh computers since the Macintosh Plus have the same mini-circular 8
pin connectors for their serial ports.
Article Change History:
23 Jun 1994 - Revised formatting and wording.
Support Information Services